A considerable number of proteins in the blood and in the body can be quantitatively determined today with immunological processes which utilize special animal serums. Although these determintion methods at the present time are applied only on a case-by-case basis in connection with certain pathological conditions and only with regard to from 3 to 5 proteins, respectively, they have produced an enrichment in diagnostic techniques, in the prevention and in the therapeutic treatment of disease. These investigations are carried out in the following manner.
Located on a transparent plate is a gel layer of from 1 to 2 mm in thickness containing the specific anti-serum. Reservoirs having a diameter of from 1 to 2 mm are stamped into the gel layer for reception of from 5 to 10 microliters of the sample. Radial precipitates are produced as a function of the concentration of the proteins to be measured, and the areas of the precipitates are proportional to the concentration of the proteins. By means of calibrated standard samples, the concentration of the substance to be determined is calculated using a regression function. The maximum diameter of the precipitates lies between 0.5 and 1.5 cm.
The disadvantages of this process reside in the fact that an evaluation is possible only after completion of the reaction (2 to 5 days). A further disadvantage is that differing results and differing variation coefficients are obtained depending upon the mathematical evaluation employed.
Furthermore, pipetting errors also influence the measurement results, because this result is directly dependent upon the volume of the substance employed. Moreover, it cannot always be assured that the precipitate has an exact circular configuration, which renders necessary a measurement of longitudinal distortion in at least two directions. The thickness of the reagent layer also influences the measured results.
It is also known to carry out reaction determinations of this type with the aid of individual, transparent glass tubes, in which the fluids to be reacted with one another are placed. This method produces more exact measurement results, since the result is nearly independent of the volume and since this method leads to quicker measurements. Disadvantageous in connection with this procedure is, however, that the tubes must be individually prepared.